The present invention relates to a composite heat shield and to a process for the production thereof. It relates more particularly to the thermal insulation of cryogenic instruments carried in spacecraft.
Heat shields are known, which are formed by the superimpositioning of a plurality of composite thermal insulants each comprising a reflecting layer or "reflector" able to reflect electromagnetic radiation and in particular infrared radiation, and a spacing layer or "spacer". The known spacers have a limited junction length between two successive reflecting layers and a limited density. Thus, they are easily compactable. As a result, there is a significant compression of the spacing layers under the effect of acceleration, vibration, etc, which leads to an increase in the number of contacting points between two successive reflectors, which increases the thermal conductivity between the reflectors joined by such spacers. This conductivity is proportional to the total weight of the elementary thermal insulants (a high number for limiting heat transmission by radiation) and consequently to the unitary surface density of the elementary thermal insulants from which the shields are formed.